external vs view into shared buffer?

Nobody has claimed this yet.

@nselliott pointed out an issue with reading external buffers in the VisIt Blueprint plugin.

The files were created with `src/axom/sidre/examples/sidre_createdatastore.cpp`
I found the issue with the VisIt plugin, however I am still a bit confused b/c I did not expect these fields to be written out as "external".

Here is the snippet that creates the views:

```
// "x", "y", and "z" are three views into a shared Sidre buffer object that
// holds 3 * nodecount doubles. These views might describe the location of
// each node in a 16 x 16 x 16 hexahedron mesh. Each view is described by
// number of elements, offset, and stride into that data.
Buffer* buff = ds->createBuffer(sidre::DOUBLE_ID, 3*nodecount)->allocate();
nodes->createView("x", buff)->apply(sidre::DOUBLE_ID, nodecount, 0, 3);
nodes->createView("y", buff)->apply(sidre::DOUBLE_ID, nodecount, 1, 3);
nodes->createView("z", buff)->apply(sidre::DOUBLE_ID, nodecount, 2, 3);
// _first_example_nodes_end
```

(With the fix) in VisIt I am definitely reading them as external views from the HDF5 file:

```
loading mesh/coordsets/coords/values/x as sidre external view
relay:io::hdf5_read domain 0 : datagroup_0000000/sidre/external/mesh/coordsets/coords/values/x
```

Is this expected? I expected them to simply be a view into a known buffer.

@kennyweiss @agcapps any thoughts?

Start with src/axom/sidre/examples/sidre_createdatastore.cpp and trace how the VisIt Blueprint plugin reads the shared-buffer views from the HDF5 paths shown in the report. Compare the expected view representation with the external-view handling, and consider the issue complete when the expected behavior is established and the plugin and stored data agree.

Written by the indexing model from the issue text.